RESUMEN
We study the motion morphology, distance, and velocity of plasma and laser-induced shock waves induced by a millisecond-nanosecond (ms-ns) combined-pulse laser with different pulse delays on silicon. The laser shadowgraph method is used, and the phenomenon of double laser-induced shock waves has been found while the pulse delay is 1.2-1.8 ms. The controlling variable method is used to study this phenomenon, and it is found that it is mainly related to the ignition of the laser-supported absorption wave induced by the ms laser. Moreover, the plasma expansion velocity increases with the increase of pulse delay, the axial propagation distance of laser-induced shock waves increases monotonically with pulse delay, and the velocity of laser-induced shock waves decreases with the increase of pulse delay.
RESUMEN
A comparative study of the interactions of the millisecond-nanosecond combined-pulse laser and millisecond pulse laser with aluminum alloy is presented. During the interaction between the laser and aluminum alloy, the coupling effect of the nanosecond pulse laser on the molten pool formed by the millisecond laser is analyzed. During the nanosecond laser irradiation in the combined approach, the expansion velocity of the plasma plume reaches 600 m/s, while the laser ablation depth increased by approximately 9 times. Based on experiments, the high-speed shadow imaging method, correlation of the temperature evolution characteristics, and ablation morphology are considered for a comprehensive analysis. The coupling effect between the millisecond-nanosecond combined-pulse laser and aluminum-alloy molten pool phase is explained.
RESUMEN
Ablation morphology affects the quality of laser processing. Therefore, the control of ablation morphology is very important. The influence of spot size combination mode on the ablation morphology of aluminum alloy is studied for the first time. Experimental results show that when the nanosecond laser spot is larger, the ablation morphology looks like a bowl-shape, and there is little solidification near the edge. When the nanosecond laser spot is smaller, the shape of the ablation morphology is similar to a hole, and the protuberance is formed near the edge of the cavity. Through the analysis and simulation of the physical model, the physical mechanism, which describes the influence of the spot size combination mode on the molten pool, is discussed. The research results of this paper have important guiding significance for the control of laser processing effect.